The present invention relates to a cross-tie for a railroad rail assembly and its method of manufacture, and, in particular, a cross-tie made from recycled tire treads.
Railroad rail assemblies use cross-ties to support the steel rails that carry freight and passenger trains. Historically the cross-ties have been made from wood, and have been treated with creosote. More recently, creosote has been classified as a carcinogen, and most localities have placed severe restrictions on its use, if not banned its use altogether. As a result, creosote-soaked cross-ties have been replaced with pressure treated timbers. Pressure treated timbers, however, have a substantially reduced life expectancy when compared to creosote timbers.
Another problem with wooden cross-ties is their inability to hold the rails they support within xe2x80x9cStandard Gaugexe2x80x9d for extended periods of time. Cross-ties must have some degree of flexibility in order to deflect under the load of a passing train, and to this extent wooden cross-ties exhibit sufficient support and durability. However, the inherent problem with any wooden tie is its limited useable life due to its tendency to decay when exposed to the elements. Consequently, degeneration of the wooden ties eventually loosens the railroad spikes, allowing the rails to move apart, which could eventually result in derailment. Therefore, the use of wooden cross-ties requires frequent maintenance and replacement. Also, the decay and breakdown of creosote soaked ties is a threat to the environment, in that State Statutes and Local Ordinances have drastically increased the cost associated with disposing of these types of cross-ties.
There have also been attempts to use reinforced concrete cross-ties and steel cross-ties to address some of the problems associated with wooden cross-ties. Concrete cross-ties, however, are expensive compared to wooden cross-ties and are not as flexible as wooden cross-ties. Concrete cross-ties have a tendency to fail under adverse conditions, at which time the cross-tie will need replacement. Accordingly, while concrete cross-ties can be used for xe2x80x9cLight Railxe2x80x9d passenger track, they are not as suitable for freight tracks due to the extreme weights inherent in freight trains.
Steel cross-ties have also been used. While steel can handle the heavy weight of freight traffic and will last for long periods of time, steel cross-ties are also expensive compared to wooden cross-ties. In order to insure the integrity of steel cross-ties, frequent inspection and welding is required thus substantially increasing their maintenance costs.
Another known cross-tie is that of U.S. Pat. No. 5,996,901 to Young. The ""901 cross-tie includes a stack of elastomeric layers (e.g., recycled tire treads) as a filler layer interposed between and fastened to a pair of rigid plates. The stack and plate assembly is held together by a plurality of wedge-shaped members and fasteners which are fixed to form non-perpendicular angles with the stack. The wedge-shaped members and bolts are positioned at multiple locations along the longitudinal (i.e., length) direction of the cross-tie.
Like the above-mentioned steel cross-ties, the ""901 cross-tie assembly is expensive. The expense is attributed not only to the inclusion of the rigid plates (e.g., steel), but also to the high number of wedge-shaped members and bolts required by the design. Ultimately, the design of the ""901 cross-time assembly is cost prohibitive.
It would be desirable to provide an environmentally friendly solution to the above-discussed problems with the prior art cross-ties. While several have attempted to provide such a solution, the expense involved has prevented any such solution from coming to fruition.
It is an object of the present invention to provide an environmentally friendly cross-tie that overcomes all the problems with the above-discussed prior art.
The present invention provides a cross-tie made of recycled tire treads stacked and secured to one another in the configuration of a traditional-sized cross-tie. The cross-tie exhibits rigidity comparable to that of wooden cross-ties, can handle the load of passenger and freight traffic, and does not present any substantial harm to the environment. Moreover, since recycled tire treads often can be obtained at a negative cost (recyclers often pay for disposal of tire treads), cross-ties can be manufactured at an expense comparable to that of wooden cross-ties.
In accordance with one embodiment of the present invention, a cross-tie for a railroad rail assembly is provided that has a first dimension extending in a first direction, a length extending in a direction substantially perpendicular to the first direction, and a second dimension extending in a second direction substantially perpendicular to the first and length directions. The cross-tie includes a plurality (n) of recycled tire treads stacked and secured to one another in one of the first and second directions, and each layer has a length substantially coextensive with the length of the cross-tie, a width substantially coextensive with one of the height and width of the cross-tie, and a thickness equal to 1/n of the other one of the height and width of the cross-tie.
In accordance with a preferred embodiment of the present invention, a cemented elastomeric membrane layer is interposed between adjacent planar layers of the cross-tie to bond the layers to one another and form an integrally bonded body. When using recycled tire treads, the cemented membrane layer includes standard cement and membrane products, which are used in the same manner as typically used to retread or recap used tires. Examples of the membrane include CHEM GUM and PC CUSHION GUM (both manufactured by Patch Rubber Company), and examples of the cement include FIBERBOND brush type cement and HV CHEMICAL CEMENT (both manufactured by Patch Rubber Company).
In accordance with another embodiment of the present invention, a railroad rail assembly is provided that includes a pair of substantially parallel rails extending in a first direction, and a plurality of cross-ties supporting the rails and extending in a direction substantially perpendicular to the first direction. Each of the cross-ties includes a plurality of recycled tire treads stacked and secured to one another either along the first direction or in a direction normal to the first direction.
In accordance with a preferred method of manufacturing the cross-tie of the present invention, a plurality of recycled tire treads, each having a length substantially coextensive with the length of the cross-tie and a width substantially coextensive with one of the height and width of the cross-tie are stacked one upon another in the other one of the height and width directions of the cross-tie, and the stacked layers are secured to one another.
Again, a cemented membrane layer is interposed between adjacent tire treads, and it is preferred to use membrane and cement products typically used to retread or recap used tires.
The cross-tie of the present invention overcomes all the problems with the prior art cross-ties described above, because it is considerably more environmentally friendly than creosote-soaked cross-ties, exhibits rigidity comparable to that of wooden cross-ties, and can be manufactured at a price that makes it comparably priced to wooden cross-ties.
Another advantage of the present cross-tie is that, since its major component is rubber, it inherently acts as a vibration damper for the rails that it supports. This vibration damping characteristic reduces rail noise and preserves the integrity of the underlying rail bed, as less vibration from passing rail cars is transmitted to the rail bed.